From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fac41,9a0ff0bffdf63657 X-Google-Attributes: gidfac41,public X-Google-Thread: f43e6,9a0ff0bffdf63657 X-Google-Attributes: gidf43e6,public X-Google-Thread: 1108a1,9a0ff0bffdf63657 X-Google-Attributes: gid1108a1,public X-Google-Thread: 103376,4b06f8f15f01a568 X-Google-Attributes: gid103376,public From: "Richard MacDonald" Subject: Re: Software landmines (loops) Date: 1998/09/03 Message-ID: <6sm7ar$nu$1@bvbsd2.kc.bv.com>#1/1 X-Deja-AN: 387484420 References: <902934874.2099.0.nnrp-10.c246a717@news.demon.co.uk> <6r1glm$bvh$1@nnrp1.dejanews.com> <6r9f8h$jtm$1@nnrp1.dejanews.com> <6renh8$ga7$1@nnrp1.dejanews.com> <6rf59b$2ud$1@nnrp1.dejanews.com> <6rfra4$rul$1@nnrp1.dejanews.com> <35DBDD24.D003404D@calfp.co.uk> <6sbuod$fra$1@hirame.wwa.com> <35f51e53.48044143@ <904556531.666222@miso.it.uq.edu.au> <6sgror$je8$3@news.indigo.ie> <6sh3qn$9p2$1@hirame.wwa.com> <6simjo$jnh$1@hirame.wwa.com> <6skcr2$i4o$1@nnrp1.dejanews.com> <6skhpr$459$1@hirame.wwa.com> X-MimeOLE: Produced By Microsoft MimeOLE V4.72.2106.4 Organization: Black and Veatch Newsgroups: comp.lang.eiffel,comp.object,comp.software-eng,comp.lang.ada Date: 1998-09-03T00:00:00+00:00 List-Id: Robert Martin wrote in message <6skhpr$459$1@hirame.wwa.com>... >Think about this for a minute. Wouldn't it be nice if you *could* stick a >line of code at the end of every loop, or at the end of every function, and >be guaranteed that it would be called? For example, have you every had to >put those interesting little print statements into functions: "entering >function x", "exitting function x"? Wouldn't it be nice if you could just >plop those print statement in without having to anlayze each and every >function for multiple returns? Very nice. Good example would be one of those cases where you are using an expensive resource (e.g., a file) and need to ensure that you close it whether or not everything worked great or it bombed. Smalltalk uses the aBlock #ensure: anotherBlock syntax, meaning no matter what happens in aBlock, anotherBlock is always executed when aBlock terminates. While this doesn't apply to loops, there are two ways to make it so: (1) Move everything in the loop to another method, then put the method in a block and apply the #do:ensure: approach to it. (2) For each loop method in the library, add another method that includes the #ensure: block. For the latter, you would want to have both pre and post ensure blocks, so this gets a little cumbersome. However, you would only have to write it (them) once, then all your code could use it (them). I've enjoyed following this discussion, but I think people are concentrating on too low a level. That is appropriate for procedural code (structured code). But we are missing higher-level solutions that OO provides us. In Smalltalk, the do loop is itself an OO method (construction). So why not add additional methods (constructions)? P.S. I like the #ensure: option, but I have measured a factor of 20 performance hit in Smalltalk when I use it.